Patent Literature 1 discloses a technique related to a light condensing unit which is used for exciting a solid-state laser. FIG. 9 is a perspective view illustrating a configuration of a light condensing unit 100 disclosed in Patent Literature 1. As illustrated in FIG. 9, the light condensing unit 100 includes two light sources 106, two optical systems 112, and a light condensing lens 114. Each of the light sources 106 has a semiconductor laser array stack 102 and a cylindrical lens stack 104. The semiconductor laser array stack 102 is configured to include a plurality of stacked semiconductor laser arrays 116 each of which has a plurality of light emission regions. The cylindrical lens stack 104 is configured to include cylindrical lenses 118 which are arranged as many as the semiconductor laser arrays 116 in a stacking direction, and is installed in the vicinity of the plurality of light emission regions of the semiconductor laser array stack 102. In addition, the optical system 112 has prisms 108 and 110. The prism 108 is a right-angle prism having a triangular prismatic shape. A side surface thereof is subjected to total reflection coating. The prism 110 is a right-angle prism having a triangular prismatic shape. A light incident surface thereof is subjected to antireflection coating, and a total reflection surface is subjected to high-reflection coating. The light condensing lens 114 has a focal point inside a solid-state laser 120 which is an excitation target of the light condensing unit 100.
In the light condensing unit 100, a laser light La1 is emitted from each of the light emission regions of the semiconductor laser arrays 116 of the semiconductor laser array stack 102. The laser light La1 is subjected to collimation by each of the cylindrical lenses 118 of the cylindrical lens stack 104, and then, the laser light La1 is reflected by two side surfaces of the prism 108, thereby being divided into a luminous flux Lb1 and a luminous flux Lc1. The luminous flux Lc1 is reflected by the two total reflection surfaces of the prism 110, and then, the luminous flux Lc1 passes over the prism 108, thereby being adjacent to the luminous flux Lb1 in a parallel manner. Thereafter, optical paths of the luminous fluxes Lb1 and Lc1 are changed by reflection mirrors 122 and 124 as necessary, and then, the luminous fluxes Lb1 and Lc1 are caused to be condensed inside the solid-state laser 120 by the light condensing lens 114.